Hi!
We are deploying a 5G network using open source platform called
"Openairinterface" (oai) and we have found a issue with oai code and
usrp model. Specifically , we think the problem is caused because OAI
uhd code tries to configure some GPIO pins in other to implement
full-duplex transmission but, as you know, USRP N321 don't have GPIO
interface. We need to use those pins to run gNB properly.
Are there any other ways to configure full-duplex mode without GPIO interface?
Please find additional information below.
Thank you in advance!
--
Sergio Pastor Tur
iTeam Research Institute
---------------------------------- Additional
info---------------------------------------
Setup description:
Linux 18.04 64 bits running on Supermicro server 32 CPU Cores and 64 GB RAM)
USRP N321
UHD version: UHD_3.14.1.HEAD-0-g0347a6d8 (additional UHD and USRP info
attached below)
---------------------------------- OAI UHD Code (full code attached
below)---------------------------------------
/*! \brief Called to start the USRP transceiver. Return 0 if OK, < 0 if error
@param device pointer to the device structure specific to the RF
hardware target
*/
static int trx_usrp_start(openair0_device *device) {
usrp_state_t *s = (usrp_state_t *)device->priv;
// setup GPIO for TDD, GPIO(4) = ATR_RX
//set data direction register (DDR) to output
s->usrp->set_gpio_attr("FP0", "DDR", 0xfff, 0xfff);
//set lower 7 bits to be controlled automatically by ATR (the rest
5 bits are controlled manually)
s->usrp->set_gpio_attr("FP0", "CTRL", 0x7f,0xfff);
//set pins 4 (RX_TX_Switch) and 6 (Shutdown PA) to 1 when the radio
is only receiving (ATR_RX)
s->usrp->set_gpio_attr("FP0", "ATR_RX", (1<<4)|(1<<6), 0x7f);
// set pin 5 (Shutdown LNA) to 1 when the radio is transmitting and
receiveing (ATR_XX)
// (we use full duplex here, because our RX is on all the time -
this might need to change later)
s->usrp->set_gpio_attr("FP0", "ATR_XX", (1<<5), 0x7f);
// set the output pins to 0
s->usrp->set_gpio_attr("FP0", "OUT", 7<<7, 0xf80);
----------------------------------------------------------------------------------------------------------------------------------------
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